Double-sided substrate cleaning apparatus and cleaning method using the same

ABSTRACT

There is provided a double-sided substrate cleaning apparatus including a carrier station for loading/unloading a carrier in which objects to be processed are stored, a convey mechanism for conveying an object taken out from the carrier station, at least one cleaning mechanism, arranged along a convey path on which the convey mechanism conveys the object, for cleaning the object, and an object reversing mechanism, arranged along the convey path, for reversing the object.

Division of application Ser. No. 08/597,536 filed on Feb. 2, 1996, nowU.S. Pat. No. 5,686,143 which is a division of application Ser. No.08/336,213, filed on Nov. 4, 1994, now U.S. Pat. No. 5,518,542.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a an apparatus for cleaning a surfaceand a back surface of an object to be processed, e.g., a semiconductorwafer (to be referred to as a wafer hereinafter), and a method using thesame.

2. Description of the Related Art A method of cleaning an object to beprocessed, e.g., a wafer, before a coating process or the like isperformed with respect thereto is disclosed in, e.g., Jpn. Pat. Appln.KOKAI Publication No. 57-90941. In this method, an object to beprocessed is rotated while it is held in a horizontal position, and aprocess solution (cleaning solution) is supplied to a surface of theobject. In addition, a brush is pressed against the surface of theobject to remove granular contaminants therefrom. Especially in acleaning process performed when a resist pattern is to be formed on anobject to be processed, both a surface and a back surface of the objectmust be cleaned in some cases. Recently, as semiconductor devicesincrease in integration density, and various types of semiconductordevices are manufactured in small quantities, surface treatment and backsurface treatment of wafers are performed in an arbitrary order.However, there is no cleaning apparatus which can cope with such variousprocesses.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an apparatus whichcan cope with various processes and quickly clean a surface and a backsurface of an object to be processed, and a method using the same.

In order to achieve the above object, there is provided a double-sidedsubstrate cleaning apparatus comprising a carrier station forloading/unloading a carrier in which an object to be processed isstored, a convey mechanism for conveying the object taken out from thecarrier station, at least one cleaning mechanism, arranged along aconvey path on which the convey mechanism conveys the object, forcleaning the object, and an object reversing mechanism, arranged alongthe convey path, for reversing the object. According to the double-sidedsubstrate cleaning apparatus having the above arrangement, various stepscan be properly handled, and a surface and a back surface of an objectto be processed can be quickly cleaned, thereby improving the throughputof various processes.

In this case, the cleaning mechanism is a surface cleaning mechanism forcleaning a surface of the object, or a back surface cleaning mechanismfor cleaning the back surface of the object. In addition, a heatingmeans for heating the object is preferably arranged along the conveypath. Furthermore, the object reversing mechanism preferably includes anorientation flat aligning mechanism for performing orientation flatalignment of the object. Moreover, the carrier station, the conveymechanism, the convey path, the object reversing mechanism, and thecleaning mechanism are preferably arranged in a single housing.

Additional objects and advantages of the invention will be set forth inthe description which follows, and in part will be obvious from thedescription, or may be learned by practice of the invention. The objectsand advantages of the invention may be realized and obtained by means ofthe instrumentalities and combinations particularly pointed out in theappended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate presently preferred embodiments ofthe invention, and together with the general description given above andthe detailed description of the preferred embodiments given below, serveto explain the principles of the invention.

FIGS. 1 and 8 are perspective views showing double-sided substratecleaning apparatuses of the present invention;

FIG. 2 is a perspective view showing a back surface brush scrubber in adouble-sided substrate cleaning apparatus of the present invention;

FIG. 3 is a view showing another structure of the brush of the backsurface brush scrubber;

FIGS. 4 and 5 are schematic views showing a megasonic nozzle in thedouble-sided substrate cleaning apparatus of the present invention;

FIG. 6 is a perspective view for explaining a structure of arotating/holding mechanism in the double-sided substrate cleaningapparatus of the present invention;

FIG. 7 is a perspective view showing a structure of an object reversingmechanism in the double-sided substrate cleaning apparatus of thepresent invention;

FIGS. 9 and 10 are schematic views for explaining a substrate processapparatus according to Example 2;

FIG. 11 is a view showing a surface cleaning process section in theapparatus shown in FIG. 9;

FIGS. 12 and 16 are views for explaining an SOG coating process sectionin the apparatus shown in FIG. 9;

FIGS. 13A to 13C are schematic views showing a coating solution supplysystem in the SOG coating process section shown in FIG. 12;

FIGS. 14, 15, 17A, 17B, and 18 are enlarged views of the main portion ofthe SOG coating process section shown in FIG. 12;

FIG. 19 is a plan view showing a main convey arm in the apparatus shownin FIG. 9;

FIG. 20 is a sectional view taken along a line 20--20 in FIG. 19;

FIGS. 21A to 21E, 22A to 22H, and 23A to 23I are sectional views forexplaining a process method according to Example 2;

FIG. 24 is a perspective view for explaining a modification of thesubstrate process apparatus according to Example 2;

FIG. 25 is a view for explaining a surface cleaning process section inthe apparatus shown in FIG. 24;

FIG. 26 is a view showing the arrangement of an apparatus for performingan ozone process to remove organic substances from an SOG film in amethod of forming an SOG film according to Example 3; and

FIG. 27 is a graph showing infrared absorption spectra showing theeffect of Example 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A double-sided substrate cleaning apparatus of the present inventionwill be described in detail below with reference to the accompanyingdrawings.

EXAMPLE 1

FIG. 1 is a perspective view showing an example of double-sidedsubstrate single sheet cleaning apparatus. A double-sided substratecleaning apparatus 1 of this embodiment includes a carrier station 3 onwhich a plurality of carriers 2, e.g., four carriers, each serving tostore a large number of wafers W can be mounted. An auxiliary arm 4 isdisposed on the central portion of the carrier station 3. The auxiliaryarm 4 serves to load/unload the wafer W into/from the carrier 2 andposition the wafer W. The double-sided substrate cleaning apparatus 1also includes a convey path, e.g., a linear transfer path 6, along whicha convey mechanism, e.g., a main arm 5, serving to pass/receive thewafer w to/from the auxiliary arm 4 can be moved in the longitudinaldirection.

On both sides of the linear transfer path 6, various process mechanismsare arranged along the linear transfer path 6. More specifically, forexample, a surface brush scrubber 7 for brushing/cleaning the surface ofthe wafer w and a back surface brush scrubber 8 for brushing/cleaningthe back surface of the wafer W are arranged side by side on one side ofthe linear transfer path 6. On the other side of the linear transferpath 6, four heating units 9 are stacked on each other. The heatingunits 9 serve to dry the wafer W. In addition, two object reversingmechanisms 10 are stacked on each other to be located next to theheating units 9.

As shown in FIG. 2, the back surface brush scrubber 8, which isincorporated in the double-sided substrate cleaning apparatus 1 havingthe above arrangement, is mainly constituted by a spin chuck 21, a jetnozzle 22, a cleaning solution spray port 23, a brush 24, anopening/closing door 26, and a cap 25. The spin chuck 21 is rotatedwhile the wafer w is held thereon in a horizontal position with acircuit pattern surface facing downward. The jet nozzle 22 serves tospray a process solution, i.e., a cleaning solution, on the uppersurface of the wafer W held by the spin chuck 21. The brush 24 serves toclean/remove granular contaminants adhering to the surface of the waferw by using a cleaning solution supplied from a cleaning solution sprayport 23 formed in the scrubber body. The opening/closing door 26 ismoved vertically and opened/closed when the wafer w is loaded/unloadedinto/from the back surface brush scrubber 8. The cap 25 is movedvertically upon opening/closing of the opening/closing door 26 so as toprevent a cleaning solution and the like from scattering in cleaning thewafer W.

As shown in FIG. 6, the spin chuck 21 has a rotating plate 32 mountedhorizontally on the upper end portion of a driving shaft 31 which isrotated by a motor 30 as a driving source. A guide plate 35 as a fluidguide means for guiding the flows of an N₂ gas, clean air, and acleaning solution to the peripheral portion of the wafer W is mountedabove a fluid outlet 31c in the driving shaft 31 at a boss portion 32aon which the rotating plate 32 is mounted. The guide plate 35 is made ofa disk-like member. Four leg portions 36 are concentrically arranged onthe lower surface of the guide plate 35. The guide plate 35 is fixed onthe boss portion 32a with screws 37 extending through the leg portions36. Holding pawls 33 for supporting the edge portion of the wafer W andholding it in a horizontal position are arranged on the outer peripheralportion of the rotating plate 32 at predetermined angular intervals.

Three slits 32b are formed in the outer circumferential portion of therotating plate 32. When the main arm 5 is moved vertically, three waferlocking pawls 5b formed on the inner circumference of a U-shaped armbody 5a pass through the slits 32b and support the wafer W. With thisoperation, the wafer W can be transferred.

For example, the driving shaft 31 is constituted by a stainless steelhollow shaft. The driving shaft 31 constitutes a fluid path 31a throughwhich a fluid flows to the back surface of the wafer W. A dirt-prooffluoroplastic tube 31b is fitted in the driving shaft 31. The drivingshaft 31 extends through the motor 30. The lower portion, of the drivingshaft 31, located on the fluid inlet side protrudes downward from thelower end of the motor 30. A seal block 42 consisting of, e.g.,stainless steel is fixed to the lower end portion of the motor 30 via aninsulating intermediate block 41 consisting of vinyl chloride. Thedriving shaft 31 is inserted into this seal block 42. In this case,first and second chambers (space portions) 44a and 44b are formed in theseal block 42. The first chamber 44a is partitioned from the motor 30via a first seal member 43a (e.g., an O-ring or a mechanical seal)mounted on the intermediate block 41. The second chamber 44b ispartitioned below the first chamber 44a via a labyrinth seal 43b servingas a second seal member which is not in contact with the outer surfaceof the driving shaft 31. The labyrinth seal 43b is mounted around thedriving shaft 31 with a small gap being ensured therebetween as follows.First, a sheet is wound on the driving shaft 31. After the labyrinthseal 43b is mounted, the sheet wound on the driving shaft 31 is removed.Since the intermediate block 41 is an insulating member, whether thelabyrinth seal is not in contact with the driving shaft 31 is checked byelectrically checking conduction between the driving shaft 31 and thelabyrinth seal 43b (specifically the seal block 42).

A fluid outlet 47 connected to a suction means such as a vacuum pump(not shown) is formed in the first chamber 44a of the seal block 42. Thesecond chamber 44b has a fluid supply port 46 which is caused tocommunicate with the fluid path 31a of the driving shaft 31 via a fluidinlet 45b and connected to a source (not shown) for supplying a fluid,e.g., a nitrogen (N₂) gas. Therefore, an N₂ gas supplied from the N₂ gassource into the second chamber 44b flows between the wafer W and therotating plate 32 through the fluid path 31a of the driving shaft 31 soas to flow in the direction of the peripheral portion of the wafer W,thereby preventing a cleaning solution supplied onto the surface of thewafer W from flowing to the back surface of the wafer W. In addition,the N₂ gas supplied into the second chamber 44b flows into the firstchamber 44a through a small gap between the labyrinth seal 43b and thedriving shaft 31. Thereafter, the N₂ gas is discharged from the fluidoutlet 47. with this arrangement, the pressure in the first chamber 44acan be set to be lower than that in the second chamber 44b. With thisejector effect, dust and the like produced at a bearing 30a of thedriving shaft 31 and adhering to the first seal member 43a aredischarged together with a discharge flow.

Note that a through hole 42a is formed in the bottom portion of the sealblock 42 in the same direction as that of the fluid path 31a of thedriving shaft 31. A transparent plate 50 consisting of, e.g., quartzglass is mounted on an opening portion of the through hole 42a. Alight-emitting element 51 is arranged above the driving shaft 31, and alight-receiving element 52 is arranged below the transparent plate 50.with this arrangement, light emitted from the light-emitting element 51is received by the light-receiving element 52. Therefore, thepresence/absence of the wafer W placed on the spin chuck 21 can bedetected by the light-emitting element 51 and the light-receivingelement 52.

The brush 24 for cleaning the wafer W is designed to be rotated aboutits axis and is fixed to one end of a brush arm 60. The other end of thebrush arm 60 is supported by a scanner 61. With the driving operation ofthe scanner 61, the brush 24 can be swung (rotated/driven) across aswing region between the wait position shown in FIG. 2 and the surface(the cleaning position) of the wafer W via the brush arm 60.

An elevating mechanism 62 for vertically moving the scanner 61 and thebrush arm 60 together is disposed under the scanner 61. When the brush24 is to be swung between the wait position and the cleaning position,the elevating mechanism 62 vertically moves the scanner 61 and the brusharm 60 together to prevent the brush 24 from colliding with the cap 25and the like. A brush cleaning unit 64 for cleaning the brush 24 set atthe wait position is disposed under the wait position of the brush 24.

As shown in FIG. 3, supply pipes 65 for supplying a cleaning solutionmay be attached to the brush 24 to be integrated with a cleaningsolution supply section. With this arrangement, the cleaning solutionsupply section need not be arranged independently, and the apparatus canbe reduced in size. In addition, since the brush 24 and the cleaningsolution supply section are integrated, a cleaning solution can beefficiently supplied to a portion brought into contact with the brush24. Although the supply pipes 65 may be attached to the brush 24, asshown in FIG. 3, a supply pipe 65 may be inserted into a rotating shaft66 of the brush 24. In addition, a cleaning operation may be performedby using the brush having the arrangement shown in FIG. 3 and the jetnozzle 22 as a cleaning solution supply section. For example, a cleaningsolution may be supplied through the supply pipes 65 shown in FIG. 3 andthe jet nozzle 22. Thereafter, the supply of the cleaning solutionthrough the supply pipes 65 or the jet nozzle 22 may be stopped, and acleaning operation may be performed again.

As shown in FIG. 2, the jet nozzle 22 is arranged on the side opposingthe brush 24 via the spin chuck 21. The jet nozzle 22 is fixed to oneend of a nozzle arm 70. The other end of the nozzle arm 70 is supportedby a scanner 71. With the driving operation of the scanner 71, the jetnozzle 22 can be swung (rotated/driven) across a swing region betweenthe wait position shown in FIG. 2 and the surface (the cleaningposition) of the wafer W.

An elevating mechanism 72 for vertically moving the scanner 71 and thenozzle arm 70 together is disposed under the scanner 71. When the jetnozzle 22 is to be swung between the wait position and the sprayposition (cleaning position), the elevating mechanism 72 verticallymoves the scanner 71 and the nozzle arm 70 together so as to prevent thejet nozzle 22 from colliding with the cap 25 and the like. In addition,a jet nozzle cleaning unit 74 for cleaning the jet nozzle 22 set at thewait position is disposed under the wait position of the jet nozzle 22.

The jet nozzle 22 is connected to a distilled water tank 77 via acleaning solution (distilled water) supply pipe 76. A pump 78 and avalve 79 are arranged midway along the cleaning solution supply pipe 76.With the pump 78 and the valve 79, a predetermined amount of distilledwater as a cleaning solution is sprayed on the wafer W. As describedabove, the jet nozzle 22 can be moved to the surface of the wafer W tospray distilled water, supplied from the distilled water tank 77, on thesurface of the wafer W. Note that a heater 80 is arranged at the outersurface side of the distilled water tank 77 to keep the temperature ofdistilled water constant. The cleaning efficiency can be improved bycleaning the wafer W using heated distilled water. If distilled water isheated, the cleaned wafer W itself is heated. Therefore, the drying timein a drying process after a cleaning process can be shortened.

The arrangement of the surface brush scrubber 7 is the same as that ofthe back surface brush scrubber 8 except that the brush scrubber 7includes a megasonic nozzle 90, as shown in FIGS. 4 and 5, instead ofthe jet nozzle 22 for spraying a process solution, e.g., a cleaningsolution, on the surface of the wafer W held by the spin chuck 21. Themegasonic nozzle 90 is designed to apply ultrasonic waves to a cleaningsolution to vibrate the solution before spraying it. More specifically,the megasonic nozzle 90 is constituted by a cleaning solution supplypipe 91 for supplying a cleaning solution, an ultrasonic oscillator 92for causing ultrasonic vibration of the supplied cleaning solution, anda spray port 93 for spraying the cleaning solution. The ultrasonicoscillator 92 is designed to cause ultrasonic vibration of a cleaningsolution within a range of, e.g., 0.5 MHz to 5 MHz. Note that theultrasonic oscillator 92 need not be arranged in the megasonic nozzle 90and may be mounted on any portion of the cleaning solution supply pipe91.

The object reversing mechanism 10 will be described next. As shown inFIG. 1, the object reversing mechanism 10 has upper and lower chambers11 and 12. As shown in FIG. 7, the lower chamber 12 has areversing/driving section 100 to be connected to a driving shaft 102extending through a side plate 101. The reversing/driving section 100 isconstituted by a driving motor 104, a driving pulley 106 fixed to amotor driving shaft 105 of the driving motor 104, a pulley 107 fixed tothe arm rotating shaft 102, and a belt 108 for coupling the two pulleys106 and 107 to each other. The arm rotating shaft 102 is rotatablyarranged via a bearing (not shown). An arm opening/closing/drivingsection 110 for opening/closing holding arms 111a and 111b by drivingthe arms is arranged on the distal end portion of the arm rotating shaft102. Arm support portions 112a and 112b as the proximal end portions ofthe pair of semicircular holding arms 111a and 111b are coupled to thearm opening/closing/driving section 110. The arm support portions 112aand 112b can be moved in the horizontal direction by a cylindermechanism (not shown).

Referring to FIG. 7, the arm support portions 112a and 112b are locatedclose to each other, so that the holding arms 111a and 111b are in aclosed state. When the arm support portions 112a and 112b are moved fromthis state by the cylinder mechanism in a direction to separate fromeach other, the holding arms 111a and 111b also separate from each otherto be set in an open state. In contrast to this, when the arm supportportions 112a and 112b are moved in a direction to come close to eachother, the holding arms 111a and 111b also come close to each other tobe set in a closed state. In this case, the closed state of the holdingarms 111a and 111b indicates a state wherein the arms are closed enoughto hold the wafer W from both sides thereof, whereas the open state ofthe holding arms 111a and 111b indicates a state wherein the arms areopened enough to release the wafer W.

In the reversing/driving section 100, when the driving motor 104 isoperated to rotate the arm rotating shaft 102 through an arbitraryangle, the arm opening/closing/driving section 110 and the holding arms111a and 111b are rotated together with the arm rotating shaft 102. Apair of shutter plates 114a and 114b are attached to two side surfacesof the arm opening/closing/driving section 110. Light-shielding typeoptical sensors (not shown) are mounted on both sides of the shutterplates 114a and 114b. The shutter plate 114b shields light from theoptical sensor in a stationary state. In performing a reversingoperation from this stationary state, when the armopening/closing/driving section 110 is rotated (reversed) through 180°,the shutter plate 114a shields light from the optical sensor. At thetiming of this light-shielding operation, the rotation of the armopening/closing/driving section 110 is stopped to be positioned. In thismanner, the holding arms 111a and 111b are rotated (reversed) through180° at a predetermined position in the lower chamber 12 by thereversing/driving section 100 and the arm opening/closing/drivingsection 110.

A spin chuck 120 for holding the wafer W in alignment of the orientationflat of the wafer W is arranged on the bottom portion of the lowerchamber 12 at a position immediately below the holding arms 111a and111b. The spin chuck 120 is rotated at a constant speed by a drivingmotor 121. The spin chuck 120 and the driving motor 121 are supported bya support member 122. The spin chuck 120, the driving motor 121, and thesupport member 122 can be vertically moved together by an elevatingmechanism 124.

A light-emitting section 125 and a light-receiving section 126constituting an optical sensor for orientation flat alignment arearranged at predetermined positions on the upper and lower portions ofthe lower chamber 12. In performing orientation flat alignment, thewafer W is placed on the spin chuck 120 and rotated, and thelight-receiving section 126 monitors light from is the light-emittingsection 125.

A plate-like wafer support base 130 is arranged between the holding arms111a and 111b and the spin chuck 120 to be movable in the verticaldirection. The wafer support base 130 is constituted by three platepieces extending from the central portion in three directions at angularintervals of 120°. Support pins 131 for supporting the edge portion ofthe wafer w vertically extend from the distal end portions of therespective plate pieces. In addition, a central opening 132 is formed inthe central portion of the wafer support base 130 to allow the spinchuck 120 to pass therethrough. The wafer support base 130 is supportedby a pair of support arms 135a and 135b extending from one side surfaceof the lower chamber 12. The support arms 135a and 135b are verticallydriven by an elevating mechanism 136 arranged on one side surface of thelower chamber 12. The elevating mechanism 136 is constituted by a block137 fixed to the proximal end portions of the support arms 135a and135b, a guide 138 for guiding the block 137 in the vertical direction,and a cylinder 140 having a piston rod 139 fixed to the block 137.

When the cylinder 140 is operated to move the piston rod 139 forward,the block 137 is lowered along the guide 138, and the support arms 135aand 135b and the wafer support base 130 are also lowered together withthe block 137. In contrast to this, when the wafer support base 130 ismoved backward, the support arms 135a and 135b and the wafer supportbase 130 are raised together with the block 137. With this drivingoperation of the elevating mechanism 136, the wafer support base 130 ismoved among the first position where the wafer w is passed/receivedto/from holding arms 111a and 111b, the second position (between thefirst and third positions) where the wafer W is passed/received to/fromthe main arm, and the third position where the wafer W can be reversedor the wafer W is passed/received to/from the spin chuck 120.

The respective components in the upper chamber 11 respectively have thesame arrangements as those in the lower chamber 12 described above,i.e., the holding arms 111a and 111b, the reversing/driving section 100,the arm opening/closing/driving section 110, the wafer support base 130,and the like, except that the upper chamber 11 includes no orientationflat aligning mechanism such as the spin chuck 120. In the upper chamber11, only a wafer reversing operation is performed.

In the double-sided substrate cleaning apparatus of the presentinvention, which has the above arrangement, when the wafer w is to becleaned, the wafer W stored in the carrier 2 mounted on the carrierstation 3 is taken out by the auxiliary arm 4. The auxiliary arm 4 ismoved to the position where the wafer w is transferred to the main arm5, and the wafer W is positioned. Thereafter, the wafer W is received bythe main arm 5. After this operation, different processes are performeddepending on whether only a surface cleaning process is performed, onlya back surface cleaning process is performed, or surface and backsurface cleaning processes are continuously performed. In thisembodiment, the process of performing a back surface cleaning operationafter a surface cleaning operation will be described.

Since the wafer W received by the main arm 5 is held with its surface(on which a pattern is formed) facing upward, a surface back/surfacereversing operation is performed by the object reversing mechanism 10.The wafer w held by the main arm 5 is then moved above the wafer supportbase 130 of the object reversing mechanism 10. Thereafter, the main arm5 is moved downward to transfer the wafer W held by the main arm 5 tothe wafer support base 130. The spin chuck 120, which has been waitingbelow the wafer support base 130, is raised through the central opening132 in the wafer support base 130, thereby receiving the wafer W. Whilethe spin chuck 120 is rotated, the light-receiving section 126 monitorslight from the light-emitting section 125 to perform orientation flatalignment. While the orientation flat is aligned, the spin chuck 120 isstopped. Thereafter, the spin chuck 120 is lowered to place the wafer Won the wafer support base 130.

The wafer support base 130 is raised to the position where the wafer Wis transferred to the holding arms 111a and 111b. At this time, theholding arms 111a and 111b are set in an open state. The holding arms111a and 111b are closed to receive the wafer W. The wafer support base130 is lowered to the position where the holding arms 111a and 111b canbe rotated. Thereafter, the holding arms 111a and 111b are rotated bythe reversing/driving section 100, thereby reversing the wafer W. Thewafer support base 130 is raised again, and the holding arms 111a and111b are opened to transfer the reversed wafer W to the wafer supportbase 130. The wafer support base 130 is lowered to the position wherewafer w can be transferred to the main arm 5. The main arm 5 receivesthe wafer W from the wafer support base 130 as though scooping it upfrom therebelow. Thereafter, the wafer W is transferred to the backsurface brush scrubber 8 by the main arm 5, and a back surface cleaningoperation is performed.

Subsequently, the wafer w held by the main arm 5 is loaded through theopening/closing door 26, which is open, and moved above the spin chuck21. The main arm 5 is then moved downward to be retreated from the spinchuck 21.

When an N₂ gas is supplied from the N₂ gas source into the secondchamber 44b via the fluid supply port 46 in the seal block 42, the N₂gas, except for part of the gas (to be described later), flows in thefluid path 31a via the fluid inlet 45b in the driving shaft 31 tocollide with the guide plate 35. The N₂ gas then flows out to the backsurface side (circuit pattern surface side) of the wafer W and flows tothe peripheral portion of the wafer W. Owing to the flow of this N₂ gas,a negative pressure is produced between the back surface of the wafer Wand the rotating plate 32 by the Bernoulli effect. The wafer W ischucked toward the rotating plate 32 side by this negative pressure tobe held on the holding pawls 33.

While the edge portion of the wafer W is held in the above-describedmanner, the motor 30 is driven to rotate the driving shaft 31 so as torotate the wafer W in a horizontal position. The brush 24 is then movedabove the wafer W, and distilled water is sprayed from the cleaninasolution spray port 23 onto the surface of the wafer W. With thisoperation, granular contaminants adhering to the surface (on which acircuit pattern is formed) of the wafer w are removed by the brush 24.In this case, the brush 24 is reciprocated between the center andperipheral edge of the wafer W to uniformly clean the entire surface ofthe wafer W. In this cleaning operation, the brush 24 is pressed againstthe wafer w while being rotated. This pressing force is set to be largerin a back surface cleaning operation than in a surface cleaningoperation. This is because a rate of removing the contaminants isimproved.

On the back surface side of the wafer W, the N₂ gas flows from thecentral portion of the wafer W to its peripheral edge. For this reason,a cleaning solution supplied to the surface of the wafer w can beprevented from flowing to the back surface of the wafer W. When thecleaning operation by the brush 24 is completed, the brush 24 is movedto the wait position, and spraying of the cleaning solution is stopped.After this operation, the jet nozzle 22 is moved to substantially thecentral position of the wafer w, and the cleaning solution is sprayedfrom the jet nozzle 22 onto the surface of the wafer W. The jet nozzle22 is reciprocated between substantially the central position andperipheral edge of the wafer w to uniformly clean the entire surface ofthe wafer W. This cleaning process may be performed by a jet cleaningoperation alone, in which a cleaning solution is sprayed from the jetnozzle 22, or by a brush cleaning operation alone, in which cleaning isperformed while a cleaning solution is supplied to a position near thebrush 24. Alternatively, the two cleaning operations may be performedalternately or simultaneously. These cleaning operations are variouslyset and performed in accordance with the type of an object to beprocessed and a cleaned state.

Part of the N₂ gas supplied into the second chamber 44b flows into thefirst chamber 44a through a small gap between the labyrinth seal 43b andthe driving shaft 31. Thereafter, the part of the gas is discharged fromthe fluid outlet 47. As a result, the pressure in the first chamber 44abecomes lower than that in the second chamber 44b. Owing to this ejectoreffect, dust and the like produced at the bearing 30a of the drivingshaft 31 and adhering to the first seal member 43a are dischargedtogether with a discharge flow, thereby preventing the dust and the likefrom adhering to the back surface, i.e., the circuit pattern surface, ofthe wafer W. In addition, entrance of the dust and the like from thefirst chamber 44a into the motor 30 can be prevented.

When the back surface cleaning process is completed in this manner, thecap 25 and the opening/closing door 26 are Lowered, and the main arm 5is inserted in a portion below the spin chuck 21. Thereafter, the mainarm 5 is moved upward to receive the wafer W. In this state, since thesurface of the wafer w faces downward, the surface and back surface ofthe wafer W are reversed by the object reversing mechanism 10. After thewafer W held by the main arm 5 is moved above the wafer support base 130of the object reversing mechanism 10, the main arm 5 is moved downward,thereby transferring the wafer W held by the main arm 5 onto the wafersupport base 130. The spin chuck 120, which has been waiting below thewafer support base 130, is then raised through the central opening 132in the wafer support base 130, thereby receiving the wafer W.Orientation flat alignment is performed by monitoring light from thelight-emitting section 125 while rotating the spin chuck 120. When theorientation flat is aligned, the spin chuck 120 is stopped. Thereafter,the spin chuck 120 is lowered to place the wafer W on the wafer supportbase 130. The wafer support base 130 is raised to the position where thewafer W is transferred to the holding arms 111a and 111b. At this time,the holding arms 111a and 111b are set in an open state. By closing theholding arms 111a and 111b, the wafer w is received by the arms. Afterthe wafer support base 130 is lowered to the position where the holdingarms 111a and 111b can be rotated, the holding arms 111a and 111b arerotated and reversed by the reversing/driving section 100. The wafersupport base 130 is raised again, and the holding arms 111a and 111b areopened to transfer the reversed wafer W onto the wafer support base 130.The wafer support base 130 is lowered to the position where the wafer Wcan be transferred to the main arm 5. The main arm 5 then passes belowthe wafer support base 130 to receive the wafer w as if the main arm 5scooped it up from below the wafer support base 130. The main arm 5transfers the wafer W to the surface brush scrubber 7. The surface brushscrubber 7 performs a surface cleaning process with respect to the waferW. After this process, the wafer W held by the main arm 5 is loadedthrough the opening/closing door 26 which is open and moved above thespin chuck 21, and the main arm 5 is moved downward and retreated fromthe spin chuck 21.

At this time, when an N₂ gas is supplied from the N₂ gas source into thesecond chamber 44b via the fluid supply port 46 in the seal block 42,the N₂ gas, except for part of the gas (to be described later), flowsthrough the fluid path 31a via the fluid inlet 45b in the driving shaft31 and collides with the guide plate 35. As a result, the gas flows outto the back surface side (circuit pattern surface side) of the wafer Wand flows to the peripheral portion of the wafer W. Owing to the flow ofthis N₂ gas, a negative pressure is produced between the back surface ofthe wafer W and the rotating plate 32 by the Bernoulli effect. The waferW is chucked toward the rotating plate 32 side by this negative pressureto be held on the holding pawls 33.

While the edge portion of the wafer W is held in the above-describedmanner, the motor 30 is driven to rotate the driving shaft 31 so as torotate the wafer W in a horizontal position. The brush 24 is then movedabove the wafer W, and distilled water is sprayed from the cleaningsolution spray port 23 onto the surface of the wafer w. with thisoperation, granular contaminants adhering to the surface (on which acircuit pattern is formed) of the wafer W are removed by the brush 24.In this case, the brush 24 is reciprocated between the center andperipheral edge of the wafer W to uniformly clean the entire surface ofthe wafer W. On the back surface side of the wafer W, the N₂ gas flowsfrom the central portion of the wafer w to its peripheral edge. For thisreason, a cleaning solution supplied to the surface of the wafer w canbe prevented from flowing to the back surface of the wafer W. When thecleaning operation by the brush 24 is completed, the brush 24 is movedto the wait position, and spraying of the cleaning solution is stopped.After this operation, the megasonic nozzle 90 is moved to substantiallythe central position of the wafer W, and the cleaning solution issprayed from the megasonic nozzle 90 onto the surface of the wafer W.The megasonic nozzle 90 is reciprocated between substantially thecentral position and peripheral edge of the wafer W to uniformly cleanthe entire surface of the wafer W. This cleaning process may beperformed by a megasonic cleaning operation alone, in which a cleaningsolution is sprayed from the megasonic nozzle 90, or by a brush cleaningoperation alone, in which cleaning is performed while a cleaningsolution is supplied to a position near the brush 24. Alternatively, thetwo cleaning operations may be performed alternately or simultaneously.These cleaning operations are variously set and performed in accordancewith the type of an object to be processed and a cleaned state.

When the surface cleaning process is completed in this manner, the spinchuck 21 is rotated to scatter the cleaning solution from the wafer W.The wafer W is then dried. After this operation, the cap 25 and theopening/closing door 26 are lowered, and the main arm 5 is insertedbelow the spin chuck 21. The main arm 5 is then moved upward to receivethe wafer W. The wafer W held by the main arm 5 is loaded into theheating unit 9. In order to dry the wafer W, the wafer W is heated, forexample, to 100° C. for 30 sec. After the heat treatment is completed,the wafer W is held by the main arm 5 again and transferred to theauxiliary arm 4. The wafer W held by the auxiliary arm 4 is returned tothe carrier 2.

The double-sided substrate cleaning apparatus of the present inventionmay be designed such that recipes can be input through a mode screen. Inthe scheme of scanning the brush 24, the jet nozzle 22, the megasonicnozzle 90, and the like, a scan time for each component can beautomatically set by setting a corresponding scan distance and scanspeed. With regard to the rotational direction of the brush 24, thefollowing three modes can be selected: a CW (clockwise) mode, a CCW(counterclockwise) mode, and a reverse mode as a combination of the CWmode and the CCW mode. In addition, the height and replacement period ofthe brush 24 and the scan range of a scan arm can be arbitrarilyadjusted. Furthermore, the object reversing mechanism 10 has a checkfunction of checking an aligning operation, a clamping operation, areversing operation, and the like step by step.

FIG. 8 shows another arrangement of the double-sided substrate cleaningapparatus of the present invention. This double-sided substrate cleaningapparatus is integrated with a coating process unit and a heat-treatmentunit, and is mainly constituted by the carrier station 3, the processsection 151, the interface section 152, and the heat-treatment section153. In the process section 151, an adhesion section 154, a bakingsection 155, a cleaning section 156, and the object reversing mechanism10 are sequentially arranged on one side of the main arm from thecarrier station 3 to the interface section 152. A coating processsection 157, a development process section 158, an exposure processsection 159, and a cleaning process section 160 are sequentiallyarranged on the other side of the main arm from the carrier station 3 tothe interface section 152.

A case wherein a resist film is formed on the wafer W in the apparatushaving the above arrangement will be described. First of all, the waferW is conveyed to the cleaning process section 160 to clean the surfaceof the wafer W. The wafer w is then conveyed to the adhesion section 154to perform an adhesion process with respect to the wafer W. The wafer wis conveyed to the cleaning section 156 to perform a cleaning processwith respect to the wafer W. Thereafter, the wafer w is conveyed to thecoating process section 157 to coat a resist solution on the wafer W.The wafer W is conveyed to the baking section 155 to perform a bakingprocess with respect to the wafer w so as to form a resist film thereon.After this process, the wafer W is conveyed to the cleaning section 156to clean the wafer W. The wafer w is conveyed to the object reversingmechanism 10 to reverse the wafer W. The reversed wafer W is conveyed tothe cleaning process section 160 to clean at least the back surface ofthe wafer W. In this manner, the back surface of the wafer W is cleanedbefore a resist film is exposed. With this process, foreign substanceshaving a size of 0.1 μm or more can be removed to improve the exposureperformance. This cleaning process is important for advancedmicropatterning.

Subsequently, the wafer W is conveyed to the object reversing mechanism10 to reverse the wafer W. The reversed wafer w is conveyed to theexposure process section 159 to clean the wafer W. The wafer W is thenconveyed to the development process section 158 to perform a developmentprocess with respect to the wafer W. Furthermore, the wafer W isconveyed to the cleaning section 156 to clean the wafer W. Thereafter,the wafer W is conveyed to the cleaning process section 160 to clean thesurface of the wafer W. In this case, if the back surface of the wafer Wis to be also cleaned, the wafer W is conveyed to the object reversingmechanism 10 to reverse the wafer W. The reversed wafer W is conveyed tothe cleaning process section 160 again to clean the back surface of thewafer W.

In this embodiment, a Bernoulli chuck using the Bernoulli effect is usedas a chuck in reversing the wafer w in the object reversing mechanism10. However, the effect of the present invention can also be obtained byusing a chuck other than a Bernoulli chuck, e.g., a mechanical chuckdisclosed in Japanese Patent Application No. 5-116390. In addition, theorder of processes in the process section 151 can be arbitrarily set. Inaccordance with the order of processes, "only a surface cleaningoperation", "only a back surface cleaning operation", and "surface andback surface cleaning operations" can be arbitrarily selected.

In the above description, an N₂ gas is used as a fluid to be supplied tothe back surface side of the wafer W through the fluid path 31a of thespin chuck 21. This fluid is not limited to an N₂ gas, but a fluid suchas another inert gas, air, or distilled water may be used. Especiallywhen a fluid such as distilled water is to be used, a branch pipe pathbranching from the cleaning solution supply pipe is preferably connectedto the fluid inlet 45b in the seal block 42. If distilled water is usedas the fluid, distilled water for preventing adhesion of a cleaningsolution (distilled water) to the back surface of the wafer W after itis held and distilled water for a cleaning operation can be suppliedfrom the same distilled water tank. Therefore, the efficiency of acleaning process can be improved, and the size of the apparatus can bereduced.

The present invention is not limited to the above processes. Forexample, the present invention can be applied to a case wherein asurface cleaning process is performed after a back surface cleaningprocess. In addition, in this embodiment, the surface of a wafer iscleaned by an ultrasonic cleaning process using the megasonic nozzle,while the back surface of the wafer is cleaned by a cleaning processusing the jet nozzle. However, the present invention is not limited tothis. For example, the surface of a wafer may be cleaned by the jetnozzle, and the back surface of the wafer may be cleaned by anultrasonic cleaning process using the megasonic nozzle.

In this embodiment, an object to be processed is the wafer W. However,the present invention can be applied to an apparatus for performing acleaning process with respect to, e.g., an LCD substrate, a photomask, aceramic substrate, a compact disk, and a printed circuit board.

EXAMPLE 2

After a substrate is cleaned in this manner, various coating processesare performed. With the recent increase in the integration density ofsemiconductor integrated circuits, the number of wiring layers stackedon each other has increased. In such a multi-layered wiring structure,an uneven lower wiring layer makes it difficult to form an upper wiringlayer. For this reason, a technique of flattening an insulatinginterlayer for insulating lower and upper wiring layers from each otheris required. As a conventional flattening technique used in forming aninsulating interlayer, a method of using SOG (Spin On Glass) is known.In this method, a solution obtained by mixing a component (e.g., asilanol compound) as a material for an insulating film and a solvent(e.g., ethyl alcohol) is coated on a wafer W having a wiring patternformed thereon, and the solvent and the like are evaporated by a heattreatment to accelerate a polymerization reaction, thereby forming aninsulating film.

In this method, if an underlayer, e.g., an SiO₂ film is exposed to theatmosphere (while the wafer W is transferred to a coating process)before an SOG solution is coated, organic substances adheres to thesurface of the SiO₂ film. As a result, the affinity between the SOGsolution and the SiO₂ film deteriorates owing to the influence of theorganic substances. For this reason, the SOG solution is coatedunevenly, or cracks tend to be produced by a heat treatment after thecoating process, resulting in a deterioration in the insulation andadhesion characteristics of the insulating interlayer.

According to this embodiment, there is provided a method and apparatuswhich can form a multilayered coating film having a good adhesioncharacteristic by removing organic substances adhering to an object tobe processed. More specifically, after a film is formed on an object tobe processed, the object is placed in an ozone atmosphere todecompose/remove organic substances adhering to the film, and a coatingsolution is coated on this film. In this method, organic substances maybe decomposed/removed by radiating ultraviolet rays on the substancesinstead of decomposing/removing the substances in an ozone atmosphere.In this case, it is preferable that ultraviolet rays be radiated on theobject while the object is heated. This organic substancedecomposing/removing process is preferably performed before the nextprocess when the object is exposed to the atmosphere in the process ofloading the object. It is further preferable that the organic substancedecomposing/removing process be performed before each coating processwhen a laminated film is to be formed.

This embodiment is characterized by comprising a surface cleaning meansfor decomposing/removing organic substances adhering to the surface ofan object to be processed, and a coating means for coating a coatingsolution on the object surface after a surface cleaning process. In theapparatus of the embodiment, the surface cleaning means preferablyincludes a means for heating an object to be processed in a surfacecleaning process.

According to this embodiment, when ultraviolet rays are radiated on afilm formed on an object to be processed, ozone (O₃) is formed fromoxygen (O₂) in the atmosphere, and oxygen radicals (O*) are alsoproduced. These ozone and oxygen radicals decompose/remove organicsubstances adhering to the film surface. Since a coating solution iscoated on the film from which the organic substances are removed in thismanner, the affinity between the coating solution and the film improvesto prevent uneven coating of the coating solution and cracks by a heattreatment after the coating process. Therefore, a multilayered coatingfilm having an excellent adhesion characteristic can be formed. In thiscase, by heating the object in the decomposing/removing process, theorganic substances can be decomposed/removed further effectively.

FIGS. 9 and 10 are schematic views for explaining an apparatus accordingto Example 2. An SOG coating/heating apparatus will be described as anexample. This SOG coating/heating apparatus is mainly constituted by acoating process section 201 for forming an SOG film (coating film) on anobject to be processed, e.g., a wafer W, by coating a coating solutionon the wafer W and drying it, a heat-treatment section 202 forperforming heat treatment of the wafer w and calcining the SOG film, andan interface section 203 for exchanging the wafer w between the coatingprocess section 201 and the heat-treatment section 202.

The coating process section 201 is constituted by a load/unload section204, a surface cleaning process section 205, an SOG coating section 206,a chemical reservoir section 207, a pre-baking process section 208, acooling process section 209, and the like. The load/unload section 204serves to load/unload the wafer W. The surface cleaning process section205 radiates ultraviolet rays on the surface of the wafer W todecompose/remove organic substances adhering to the surface. The SOGcoating section 206 coats an SOG solution on the surface of the wafer wby, e.g., spin coating. The chemical reservoir section 207 is used tostore an SOG solution or the like used by the SOG coating section 206.The pre-baking process section 208 heats the wafer W at a predeterminedtemperature after an SOG solution is coated on the wafer W, therebydrying the SOG solution. The cooling process section 209 cools the waferW to a predetermined temperature. Since a method of removing organicsubstances by using ozone generated by radiating ultraviolet rays isdisclosed in Jpn. Pat. Appln. KOKAI Publication No. 61-290724, adetailed description thereof will be omitted. A main convey path 210 isarranged in the central portion of the coating process section 201. Amain convey handler 211 is arranged in the main convey path 210 to bemovable in the horizontal direction (indicated by arrows X and Y in FIG.9), the vertical direction (indicated by an arrow Z), and the rotationaldirection (indicated by an arrow θ). The respective process sections 205to 209 are arranged on both sides f the main convey path 210.

The load/unload section 204 includes carrier cassettes 212 and 213arranged in a line in the Y direction, and a wafer holding arm 214. Thecarrier cassettes 212 are used to store unprocessed wafers W (an SiO₂film as an underlayer is formed on the wiring pattern formation surfaceof each wafer by a plasma CVD method) on which no SOG films are formed.The carrier cassettes 213 are used to store processed wafers W. Thewafer holding arm 214 is designed to be movable in the arrangingdirection (the Y direction in FIG. 9) of the carrier cassettes 212 and213, the horizontal direction (the X direction), and the verticaldirection (the Z direction). This arm 214 serves to load/unload thewafers W into/from the carrier cassettes 212 and 213. A transfer base215 for transferring the wafer w between the wafer holding arm 214 andthe main convey handler 211 is arranged near one end portion of the mainconvey path 210 of the load/unload section 204.

As shown in FIG. 11, the surface cleaning process section 205 issubstantially constituted by an electric heating type hot plate 217,which uses a nichrome wire heater, and an ultraviolet lamp 218. The hotplate 217 is arranged near the bottom portion of a process chamber 216.The ultraviolet lamp 218 is arranged near the ceiling portion of theprocess chamber 216. In this case, the ultraviolet lamp 218 isconstituted by two ultraviolet lamp bodies 218a (emission wavelength:184 nm) and 218b (emission wavelength: 254 nm) for emitting ultravioletrays having different emission wavelengths. An O₂ supply port 216aconnected to an oxygen (O₂) source 219 is formed in one side wall of theprocess chamber 216. An outlet 216b is formed in the side wall opposingthe O₂ supply port 216a. A wafer entrance 216c (see FIG. 9) of theprocess chamber 216 is hermetically sealed by an automaticopening/closing shutter (not shown). After the wafer w is placed on thehot plate 217 by the main convey handler 211, the wafer entrance 216c isclosed by the shutter, and O₂ is introduced into the process chamber216.

In the surface cleaning process section 205 having the abovearrangement, while the wafer w is heated to a predetermined temperatureby the hot plate 217, ultraviolet rays can be radiated from theultraviolet lamp 218 (specifically the ultraviolet lamp bodies 218a and218b) onto the surface of the wafer W. In this case, the wafer w isheated to, e.g., 100° C. by the hot plate 217, and O₂ supplied into theprocess chamber 216 is converted into ozone (O₃) by ultraviolet rayshaving a wavelength of 184 nm, which is emitted from the ultravioletlamp body 218a. This ozone is then excited and activated by ultravioletrays having a wavelength of 254 nm, which is emitted from theultraviolet lamp body 218b, to produce oxygen radicals (O*), therebyremoving organic substances by using this oxygen radicals. This processcan be performed for several tens seconds.

As shown in FIGS. 12 and 13A to 13C, the main portion of the SOG coatingsection 206 is constituted by a spin chuck 220 for holding the wafer Wby vacuum suction and rotating it horizontally, a process cap 221 havinga cylindrical shape with a bottom and enclosing the spin chuck 220, anozzle convey arm 223 for selectively moving a supply nozzle 225 for,e.g., an SOG solution to a position above the spin chuck 220 or a nozzlewait section 222, and an arm moving mechanism 224 for moving the nozzleconvey arm 223.

The lower end portion of the spin chuck 220 is fixed to a rotating shaft227 of a motor 226 for rotating the spin chuck 220 and the wafer W at apredetermined rotational speed. The process cap 221 is constituted by aninner cap 228 concentrically arranged to surround a wafer holdingsection 220a of the spin chuck 220, and an outer cap 229 for housing thespin chuck 220 and the inner cap 228 and forming an internal processspace. An exhaust port 230 and a liquid discharge port 231 are formed inthe bottom portion of the outer cap 229. An exhaust unit (not shown) isconnected to the exhaust port 230 via a pipe 232 so that a scattered SOGsolution and particles in coating the SOG solution on the wafer W can bedischarged through the exhaust port 230 together with the atmosphere inthe SOG coating section 206. A discharged liquid tank (not shown) isconnected to the liquid discharge port 231 via a pipe 233 so that an SOGsolution and the like which flow downward along the inner surface of theouter cap 229 and the inner cap 228 and are stored in the bottom portionof the outer cap 229 can be discharged and recovered through the liquiddischarge port 231.

An SOG solution which is thrown and scattered upon rotation of the waferw adheres to the inner surface of the process cap 221. If this state isleft as it is, the SOG solution is crystallized and solidifies toproduce particles or disturb the flow of air in the process cap 221,resulting in a deterioration in coating uniformity. For this reason, thescattered SOG solution must be properly cleaned and removed. For thispurpose, as shown in FIG. 14, slit-like cleaning solution outlets 235for allowing a cleaning solution 234 such as isopropyl alcohol (IPA) toflow downward to an inner surface 220a of the outer cup are formed in anupper opening edge portion 229b of the outer cap 229, throughout theentire circumference, at proper angular intervals. In addition,slit-like cleaning solution outlets 236 for allowing the cleaningsolution 234 to flow downward to an outward inclined surface 228a of theinner cap 228 are formed in the upper end portion of the inner cap 228,throughout the entire circumference, at proper angular intervals. Thesecleaning solution outlets 235 and 236 respectively communicate withannular solution reservoir portions 237 and 238 formed in the outer andinner caps 229 and 228. By supplying the cleaning solution 234 from acleaning solution source (not shown) to the solution reservoir portions237 and 238 via a temperature adjusting means and a flow rate adjustingmeans, the cleaning solution 234 can be sprayed from the cleaningsolution outlets 235 and 236 at a proper flow rate and a propertemperature. A cleaning process for the process cap 221, which isperformed by causing the cleaning solution 234 to flow downward, isperformed every time, for example, coating of an SOG solution on is onewafer w is completed. Note that members such as a base member 240 in theinner cap 228, which are easily corroded by an organic solvent such ascyclohexanone used for cap cleaning, side rinsing, back rinsing, and thelike and hence are difficult to clean are preferably subjected to aTuframe process to improve in chemical resistance. As a component, e.g.,an air pipe such as an air cylinder, arranged near the process cap 221,to which an SOG solution may adhere, for example, a fluoroplastic tubewhich is resistant to cyclohexanone is preferably used.

As shown in FIG. 15, the connecting portion between the exhaust port 230(liquid discharge port 231) of the process cap 221 and the pipe 232(233) is designed such that a jacket member 244 mounted on the distalend of the pipe 232 (233) is fitted and fixed on a nozzle 242 mounted onthe exhaust port 230 (liquid discharge port 231). A dam 245 having thesame inner diameter as that of the pipe 232 (233) is arranged in thejacket member 244 so that a liquid reservoir groove 246 is formed alongthe inner surface of the jacket member 244. In addition, a cleaningsolution supply pipe 247 for supplying the cleaning solution 234 to theliquid reservoir groove 246 extends through a wall portion of the jacketmember 244. The cleaning solution 234 is supplied from a cleaningsolution source (not shown) to the liquid reservoir groove 246 via thecleaning solution supply pipe 247, and the cleaning solution graduallyoverflows the dam 245. With this operation, the cleaning solution 234 iscaused to flow downward to the entire inner surface of the pipe 232(233) to constantly perform a cleaning operation.

As shown in FIG. 13A, the SOG solution supply nozzle 225 is connected toan SOG solution tank 251 via an SOG supply pipe 250. A pressure gassupply controller 252 is connected to the SOG solution tank 251. Thepressure gas supply controller 252 pressurizes and supplies an SOGsolution into the SOG solution tank 251 while controlling the flow rateof helium (He) as a pressure gas. when the pressure gas supplycontroller 252 is operated, and an opening/closing valve 253 arrangedmidway along the SOG supply pipe 250 is opened, an SOG solution 254 inthe SOG solution tank 251 is supplied to the supply nozzle 225 via theSOG supply pipe 250 and supplied (e.g., dropped) onto the wafer W heldby the spin chuck 220. As a pressure gas supply pipe 257 for the SOGsupply pipe 250 and the pressure gas supply controller 252, a syntheticresin tube, e.g., a fluoroplastic tube, is used in consideration ofchemical resistance to cyclohexanone. The SOG solution tank 251 and thepressure gas supply controller 252 are arranged in the chemicalreservoir section 207 adjacent to the SOG coating section 206. Thetemperature of the SOG solution 254 in the SOG solution tank 251 is keptat about 10° C. by a temperature adjusting means (not shown) in thechemical reservoir section 207. A heat exchanger 255 as a temperatureadjusting means for adjusting the temperature of the SOG solution 254,which is supplied for a coating process, to, e.g., about 23° C. isarranged midway along the SOG supply pipe 250 near the supply nozzle225. The heat exchanger 255 circulates temperature-adjusted water 256 ina heat exchanger body 255a accommodating part of the SOG supply pipe250, thereby performing heat exchange between the temperature-adjustedwater 256 an the SOG solution 254 via the tube wall of the SOG supplypipe 250. Note that a temperature adjusting means similar to the abovemeans is preferably arranged for the supply nozzle 225. In addition, forexample, a conductive tape 258 is wound around another portion of theSOG supply pipe 250. This conductive tape 258 is grounded to a bodyframe 260 or the like of an insulating interlayer forming unit via aconductive line 259. With this arrangement, charging of the SOG solution254 supplied to the SOG supply pipe 250 and the wafer w can be preventedto prevent adhesion/mixture of particles by static electricity. Inaddition, an antistatic film may be coated/formed on the surface of theSOG supply pipe 250.

As shown in FIG. 16, in this SOG coating section 206, clean air 267which is introduced into a process section body 206a via a ventilationpipe 264 can be caused to flow downward via a filter 265 arranged on theceiling portion and can be forcibly exhausted through the bottom portionby a fan 266. With this arrangement, the SOG coating section 206 canalways perform a process in a clean atmosphere. In this case, asindicated by the chain line in FIG. 16, the bottom portion of theprocess section body 206a may be connected to the ventilation pipe 264to form a circulation path, and a temperature adjusting unit 270 and amoisture preventing unit 271 may be arranged in this circulation path,thereby circulating/supplying the clean air 267 whose temperature andmoisture are adjusted to constant values. In addition, an air flowdetector (not shown) is preferably arranged near the lower surface ofthe filter 265 so that the outlet amount of the clean air 267 can beautomatically adjusted.

The nozzle wait section 222 of the SOG coating section 206 includes anozzle holding section 276, a dummy dispensing section 277, and a waitsection 278. The nozzle holding section 276 serves to hold the nozzlewhich is not used. The dummy dispensing section 277 causes the supplynozzle 225 in use, which is held by the nozzle convey arm 223, todischarge the SOG solution 254, in a predetermined amount, other than asolution actually used for a coating process, and discards the SOGsolution which has changed in quality. The dummy dispensing section 277also serves to prevent clogging of the supply nozzle 225. The waitsection 278 allows the supply nozzle 225 in use to temporarily wait.Note that a side rinsing nozzle wait section 222A fordissolving/removing an SOG solution coated on the peripheral portion ofthe wafer W is arranged on the opposite side of the spin chuck 220 tothe nozzle wait section 222.

As shown in FIG. 17A, the dummy dispensing section 277 is constituted byan annular block 279 having a double structure constituted by inner andouter members. A through hole 280 is vertically formed in the annularblock 279. The supply nozzle 225 is inserted into the through hole 280and caused to spray the SOG solution 254, and the SOG solution 254 isdischarged via a liquid discharge pipe 284 connected to the lower endportion of the through hole 280. A chemical-resistant material such as afluoroplastic material is used for an inner member 281 of the annularblock 279 and the inner member 281. An annular liquid reservoir groove282 is formed in the inner member 281 with its inner wall portion beingleft as a dam 283. A cleaning solution supply path 285 for supplying thecleaning solution 234, e.g., IPA, to the liquid reservoir groove 282extends through the wall portion of the annular block 279. The cleaningsolution 234 is supplied from a cleaning solution source (not shown) tothe liquid reservoir groove 282 via the cleaning solution supply path285, and the cleaning solution gradually overflows the dam 283, therebycausing the cleaning solution 234 to uniformly flow downward to theentire inner surface of the liquid discharge pipe 284. With thisoperation, a cleaning process can be performed. A purge gas introducingflow path 286 and a discharge flow path 287 are symmetrically formed atthe nozzle insertion position of the annular block 279 to extend throughthe wall portion of the annular block 279. By supplying a clean purgegas such as a nitrogen (N₂) gas around the supply nozzle 225, a dummydispensing process can be performed in a clean atmosphere.

This dummy dispensing section 277 is also used to clean a portion aroundthe supply nozzle 225. In this case, for example, as shown in FIG. 17A,a cleaning solution supply pipe 288 is connected to a side portion of anozzle body 225a, and a cleaning solution from the cleaning solutionsupply pipe 288 is supplied and caused to flow downward to the proximalend portion of the supply nozzle 225 via a flow path 289 in the nozzlebody 225a, thereby cleaning a portion around the supply nozzle 225. Inaddition, as shown in FIG. 18, a jacket 290 made of a tubular member iscoaxially arranged around the supply nozzle 225, and the distal end ofthe supply nozzle 225 is caused to communicate with the jacket 290 via acommunication path 290a. In this arrangement, by supplying a cleaningsolution to the distal end portion of the supply nozzle 225, a portionaround the supply nozzle 225 can be effectively cleaned.

As shown in FIG. 17B, a wait section 278 is constituted by a tank block291 having a double structure constituted by inner and outer members. Asolvent supply flow path 293 for supplying an organic solvent, e.g.,ethyl alcohol as a solvent for SOG, into a tank 292 extends through awall portion near a bottom portion 291a of the tank block 291. Inaddition, a solvent discharge flow path 294 extends through a wallportion, of the tank block 291, located near the insertion position ofthe supply nozzle 225. A solvent 295 is supplied from a cleaningsolution source (not shown) into the tank 292 via the solvent supplyflow path 293 and caused to flow out from the solvent discharge flowpath 294. With this operation, the amount of the solvent 295 stored inthe tank 292 can always be kept constant. Therefore, when the supplynozzle 225 is inserted into the tank 292, and an upper opening portion292a is sealed by the nozzle body, a space above a solvent liquid level295a in the tank 292 is filled with a saturation atmosphere of thesolvent 295, thereby preventing an SOG solution at a nozzle distal endportion 225b from solidifying during a wait period.

The pre-baking process section 208 is constituted by a plurality (fourin this case) of heat-treatment units 261 stacked on each other. Eachheat-treatment unit 261 has an electric heating type hot plate forheating the wafer W while it is placed thereon. One wafer w is loadedinto each heat-treatment unit 261 to heat the wafer w, thereby drying anSOG solution coated on the wafer surface. In this case, the processtemperature is set to be 100 to 140° C.; and the process time, about 1to 5 min.

The cooling process section 209 is constituted by a plurality (two inthis case) of cooling process units 262 stacked on each other. Eachcooling process unit 262 has a water-cooling type cool plate (not shown)for cooling the wafer W while it is placed thereon. The wafers W heatedby the surface cleaning process section 205 and the pre-baking processsection 208 are loaded, one by one, into the cooling process units 262.Each cooling process unit 262 can cool the wafer W to room temperature,e.g., about 22° C.

For example, two main convey handlers 211 are respectively arranged atupper and lower positions. The two main convey handlers 211 can bedriven independently. As shown in FIGS. 19 and 20, each main conveyhandler 211 has a wafer support frame 268 having a partially notchedannular shape. Pawls 269 are formed at three portions of the wafersupport frame 268, i.e., the two end portions and proximal end portionof the wafer support frame 268. The pawls 269 are engaged with the edgeportion of the wafer W to support the wafer. These pawls 269 positionthe wafer W by causing the wafer W to drop on inclined surfaces 269aformed on the inside portions of the pawls 269, thereby preventing thewafer W from shifting while it is conveyed. By using these two handlers,two wafers W can be concurrently loaded/unloaded into/from therespective process sections 205 to 209. Consequently, the processefficiency can be improved. In addition, as a material for the pawls 269of the main convey handlers 211, a polyimide resin having a highstrength and a high heat resistance is preferably used.

The interface section 203, which is adjacent to the coating processsection 201 and serves to load/unload the wafer W into/from theheat-treatment section 202, includes an intermediate transfer base 296located near an end portion of the main convey path 210 and having apositioning function. In the interface section 203, a plurality (threein FIGS. 9 and 10) of quartz wafer boats 297 are detachably mounted,together with a dummy wafer boat 297a, on a movable base 298 which ismovable in the Y direction with respect to the surface of theheat-treatment section 202. In each wafer boat, wafers W arerespectively arranged/held in multiple stages in the vertical direction.The dummy wafer boat 297a serves to replenish each wafer boat 297 withdummy wafers. In addition, a transfer/convey mechanism 299 is arrangedbetween the intermediate transfer base 296 and the movable base 298. Thetransfer/convey mechanism 299 is constituted by a convey path 300extending in the arranging direction of the wafer boats 297, and aconvey arm 301, arranged in the convey path 300 to be movable in the X,Y, Z, and θ directions, for conveying the wafer W which has undergone acoating process and is placed on the intermediate transfer base 296 intothe wafer boat 297. Note that an entrance 303 is formed in a sideportion of the interface section 203. An operator can go into and getout of the interface section 203 through the entrance 303.

The heat-treatment section 202 includes a boat elevator (not shown), aheat-treatment furnace 304, and a boat convey arm 302. The wafer boat297 is placed on the boat elevator to be movable in the verticaldirection. The heat-treatment furnace 304 is arranged above the boatelevator. The heat-treatment furnace 304 includes a quartz process tube305, having an elongated cap-like shape, for storing the wafer boat 297on the boat elevator, and a heater (not shown) outside the quartzprocess tube 305. The boat convey arm 302 serves to exchange the waferboat 297 between the movable base 298 in the interface section 203 andthe boat elevator via an opening window 304a. In the heat-treatmentsection 202, the heating temperature is set to be about 400° C.; and theprocess time, about 30 to 90 min.

A process of forming an insulating interlayer (SOG film) by using theapparatus of this embodiment having the above arrangement will bedescribed next with reference to FIGS. 21A to 21E.

The load/unload section 204 of the coating process section 201 receivesthe carrier cassettes 212, each storing a predetermined number of wafersW. A wiring pattern 310 and an SiO₂ film 311 (underlayer) are formed onthe surface of each wafer w by a plasma CVD apparatus and a wiringpattern forming apparatus (none are shown) installed at positionsdifferent from that of the coating process section 201. The waferholding arm 214 of the load/unload section 204 takes out these wafers Wfrom the carrier cassette 212 one by one, and passes them to the mainconvey handler 211 via the transfer base 215.

Each wafer w is conveyed first to the surface cleaning process section205 by the main convey handler 211. In this section, the wafer W isheated to almost 100° C. on the hot plate 217 and irradiated withultraviolet rays emitted from the ultraviolet lamp 218. with thisoperation, the bonds of carbons (C) in the SiO₂ film are decomposed. Atthe same time, O₂ is converted into ozone by ultraviolet rays emittedfrom, e.g., the ultraviolet lamp body 218a (emission wavelength: 184nm), and oxygen radicals (O*) are produced by ultraviolet rays emittedfrom the ultraviolet lamp body 218b (emission wavelength: 254 nm). Anorganic substance 312 adhering to the surface of the SiO₂ film 311 issubjected to ashing and decomposed/removed by these oxygen radicals upona chemical reaction (FIG. 21A). This surface cleaning process isperformed very efficiently owing to the synergistic effect of radiationof ultraviolet rays and heating. Thereafter, the wafer W is conveyed tothe cooling process section 209 to cool the wafer W to room temperature(FIG. 21B). The wafer W is transferred to the spin chuck 220 of the SOGcoating section 206. While the wafer w is rotated at a predeterminedrotational speed, the SOG solution 254 is dropped from the supply nozzle225 onto the surface of the SiO2 film 311, thereby coating the SOGsolution 254 on the surface (FIG. 21C). At this time, the SOG solution254 is dropped while the supply nozzle 225 is scanned in the radialdirection of the wafer W. After this operation, the wafer W is conveyedto the pre-baking process section 208, in which the wafer W is heatedto, e.g., 120° C. to evaporate and dry the solvent of the SOG solution254, thereby forming an SOG film 313 (FIG. 21D).

After the process performed by the coating process section 201, thewafers W are transferred from the main convey handler 211 to the conveyarm 301 of the interface section 203 via the intermediate transfer base296, and are sequentially stored in the wafer boat 297. After apredetermined number (e.g., 50) of wafers W are set in the wafer boat297, together with a total of 10 dummy wafer, i.e., five dummy wafersset above or below the wafers w, the wafer boat 297 is placed on theboat elevator by the boat convey arm 302. The boat elevator is raised toplace the wafer boat 297 in the quartz process tube 305. In theheat-treatment furnace 304, the wafer boat 297 is externally heatedwhile a purge gas is introduced into the quartz process tube 305,thereby performing a heat treatment, e.g., curing, with respect to theSOG films 313 on the wafers w held by the wafer boat 297 altogether(FIG. 21E).

After this heat treatment, the wafer boat 297 is taken out from theheat-treatment section 202 by the boat convey arm 302 and returned tothe movable base 298 of the interface section 203. With a reverseoperation to the above operation, the wafer w is transferred to the mainconvey handler 211 of the coating process section 201. The wafer W isthen transferred to the wafer holding arm 214 on the transfer base 215of the load/unload section 204 to be stored in the carrier cassette 213.

After the organic substance 312 on the surface of the SiO₂ film 311 isdecomposed/removed by radiating ultraviolet rays on the wafer W, the SOGsolution 254 is coated on the SiO₂ film 311. with this operation, theaffinity between the SOG solution 254 and the SiO₂ film 311 is improvedto prevent uneven coating of the SOG solution 254 and cracks caused by adrying and curing processes after the coating process. Therefore, aninsulating interlayer (SiO₂ film) 313 having good insulation andadhesion characteristics can be formed.

Assume that the SOG solution 254 cannot be coated thick on the surfaceof the SiO₂ film 311 at once. In this case, first of all, a surfacecleaning process and a cooling process (FIGS. 22A and 22B) areperformed. An SOG solution coating process and a drying process are thenperformed to form a first SOG film 313a (FIGS. 22C and 22D). Thereafter,ultraviolet rays are radiated on the wafer W to decompose/remove theorganic substance 312 (the residual organic substance of the SOG film313a in this case) on the surface of the first SOG film 313a (FIG. 22E).An SOG solution coating process and a drying process are performed againto form a second SOG film 313b (FIGS. 22F and 22G), and a curing processis performed (FIG. 22H), thereby obtaining an insulating interlayer(SiO₂ film) 313 having a good adhesion characteristic and apredetermined thickness.

An insulating interlayer (SiO₂ film) 313 having a good adhesioncharacteristic and a predetermined thickness can also be obtained in thefollowing manner, as shown in FIGS. 23A to 23I. After a drying processis performed with respect to the first SOG film 313a (FIG. 23D), acuring process is performed (FIG. 23E). Ultraviolet rays are radiated onthe wafer w to decompose/remove the organic substance 312 on the surfaceof the first SOG film 313a (FIG. 23F). An SOG solution coating processand a drying process are performed again to form the second SOG film313b (FIGS. 23G and 23H). Thereafter, a curing process is performedagain (FIG. 23I). Note that the steps in FIGS. 23A to 23C are the sameas those in FIGS. 22A to 22C.

This embodiment is most suitable for the formation of an inorganic SOGfilm. In the embodiment, ultraviolet rays are radiated on an underlayer,i.e., an SiO₂ film or an SOG film as an undercoating, formed on thewafer W surface to produce ozone and oxygen radicals so as todecompose/remove organic substances on the underlayer or the SOG film asthe undercoating. Especially when an organic SOG film is to be formed,ozone may be directly supplied to the wafer W surface, without using anultraviolet lamp, to decompose/remove organic substances. Morespecifically, as shown in FIGS. 24 and 25, for example, an ozonegenerating unit 321 using corona discharge is connected to the processchamber 216 of the surface cleaning process section 205 via an ozonesupply pipe 320. Ozone generated by the ozone generating unit 321 issupplied into the process chamber 216 to decompose/remove organicsubstances in an underlayer (SiO₂ film) or an SOG film (especially anorganic SOG film) on the wafer w surface. In addition, since ozone (O₃)and oxygen radicals (O*) give no ion impact to a film upon reactionswith organic substances, the organic substances can be removed withoutadversely affecting the film quality, unlike in ion etching. Inaddition, ozone (O₃) and oxygen radicals not only remove the residualorganic substance in the SOG film but also increase the number of bondsof Si and O, and hence give no adverse effect on the SOG film. Note thatthe portions in FIGS. 24 and 25 other than that described above are thesame as those in FIGS. 9 and 10. Therefore, the same reference numeralsin FIGS. 24 and 25 denote the same parts as in FIGS. 9 and 10, and adescription thereof will be omitted.

In the case wherein an object to be processed is loaded into aheat-treatment furnace, installed at a different position, after acoating process, if a long period of time elapses before the object isloaded into the heat-treatment furnace, since the SOG is hygroscopic andorganic substances are dissociated in the SOG film, the hygroscopicityof the object further increases. In order to prevent such a phenomenon,for example, the SOG film is preferably made to have a hydrophobicnature by adhering hexamethyldisilane to the SOG film as the objectafter a coating process.

In this example, an insulating interlayer is formed on the wafer w bycontinuously performing a coating step and a heat-treatment step. Theprocess method and apparatus of this example can also be applied to acase wherein a similar insulating interlayer is formed on an LCDsubstrate or the like. In addition, this example can be applied to onlya coating step. Furthermore, in processing an object to be processed,which has been exposed to the atmosphere, by loading it into a processsection, this example can be applied to a case wherein the objectsurface is set in an ozone atmosphere or in a surface cleaning processsection using ultraviolet radiation before the above process isexecuted.

EXAMPLE 3

As described above, SOG includes organic SOG basically containing anorganic component, and inorganic SOG basically containing no organiccomponent. Although an inorganic SOG film has a dense compositionconsisting of only inorganic substances and hence is low inhygroscopicity, it tends to shrink owing to a stress generated upon acuring process. For this reason, it is difficult to form a thick film byone coating step, and coating must be performed twice to form a thickfilm. In contrast to this, since an organic SOG film is not easilycaused to shrink by a stress generated by a curing process, a thick filmcan be obtained by one coating step. However, the organic SOG film tendsto deteriorate in film quality because it contains organic substances.In addition, organic substances are deposited on the surface of the SOGfilm owing to an etching back effect. More specifically, in etching backof an SOG film, although a reaction product produced by an etching gas,e.g., a CF₄ gas, and inorganic SiO in the SOG film is gasified, theetching gas and organic substances do not basically cause any reaction.Even if a reaction is caused, the reaction product (organic compound) isnot gasified but remains as it is. Therefore, organic substances areinevitably deposited on the surface of the SOG film, even though thethickness of the deposition film is on the micron order. If a plasma CVDfilm is formed on such an organic deposition film in the next step, theadhesion of each film deteriorates. Consequently, the films can beeasily separated from each other.

In order to remove organic substances deposited on the surface of theSOG film after etching back, a general ashing method using an oxygenplasma may be used. In this ashing method, however, since organicsubstances are removed by a physical force, i.e., by radiating a plasmaor ions on an SOG film, damage such as a crystal defect may be caused tothe SOG film. In addition, even if organic substances are simply removedfrom the surface of the SOG film by an ashing process, organicsubstances still remain in the film. Therefore, the film quality itselfcannot be improved.

This example has been made in consideration of the above problem, andhas as its object to improve the film quality of an SOG film byeffectively removing organic substances not only from the film surfacebut also from the inside of the film without damaging the SOG film. Morespecifically, this example is characterized by comprising the first stepof coating an SOG film on a predetermined underlying film, the secondstep of curing the SOG film by annealing after the first step, the thirdstep of flattening the surface of the SOG film by etching back the SOGfilm after the second step, and the fourth step of removing organicsubstances from the SOG film by exposing the SOG film to an ozoneatmosphere while heating it to a predetermined temperature after thethird step. In the addition, this example is characterized by comprisingthe first step of coating an SOG film on a predetermined underlyingfilm, the second step of removing organic substances from the SOG filmby exposing the SOG to an ozone atmosphere while heating it to apredetermined temperature after the first step, and the third step ofcuring the SOG film by annealing after the second step.

The present inventors have found the following important fact. When anSOG film was exposed to an ozone atmosphere while it was heated to apredetermined temperature, oxygen radicals produced by thermaldecomposition of ozone chemically reacted with organic substances in theSOG film as well as organic substances on the surface of the SOG film.Owing to the reaction in the film, inorganic substances recombined witheach Is other at portions from which organic substances are removed. Asa result, the chains of the bonds of inorganic substances were elongatedto improve the quality of the SOG film. Therefore, according to thefirst aspect of this example, in the fourth step, organic substancesdeposited on the surface of the SOG film in the third step (etching backstep) are removed by a chemical reaction between the oxygen radicals andthe organic substances. In addition, according to the second aspect ofthis example, in the second step, organic substances as stains adheringto the surface of the SOG film are removed by a chemical reactionbetween the oxygen radicals and the organic substances, and at the sametime, organic substances in the film are removed. Therefore, the SOGfilm is cured in the third step (annealing step) while it contains no orlittle organic substances. In this example, since organic substances areremoved from an SOG film by a chemical reaction of an oxygen radicalwithout giving no physical impact to the film, there is no possibilityof damage to the SOG film.

FIG. 26 schematically shows the arrangement of an apparatus forperforming an ozone process to remove organic substances from an SOGfilm by using the above method of this example. This apparatus includesa process chamber or vessel 410 which can be sealed. A disk-like heatplate 412 as a mount base is arranged in the center of the processchamber 410. The heat plate 412 is made of a metal having a high thermalconductivity, e.g., aluminum. The wafer W having an SOG film is placed,as an object to be processed, on the upper surface of the heat plate412. In the process chamber 410, the heat plate 412 incorporates aheater, e.g., a heating resistive element 414, for heating the wafer,and a gas introduction chamber 416 for supplying ozone as a process gasor an atmospheric gas to the wafer W is arranged outside the heat plate412 in the circumferential direction.

An oxygen source 418, an ozone generator 420, and a gas flow ratecontrolling unit 422 are arranged outside the process chamber 410 to beconnected in series with the gas introduction chamber 416 of the processchamber 410 via a pipe 424. The oxygen source 418 serves to supplyoxygen as a material for ozone. The ozone generator 420 generates ozoneby using oxygen supplied from the oxygen source 418. The gas flow ratecontrolling unit 422 controls the flow rate of ozone supplied to theprocess chamber 410. An opening/closing valve 426 is arranged midwayalong the pipe 424. An exhaust port 410a is formed in the centralportion of the ceiling of the process chamber 410. An exhaust unit 430constituted by a vacuum pump is connected to the exhaust port 410a via apipe 428.

Ozone supplied from the ozone generator 420 into the gas introductionchamber 416 in the process chamber 410 via the pipe 424 is uniformlysprayed from many gas spray ports 416a, formed in the upper surface ofthe gas introduction chamber 416 at a predetermined pitch, at apredetermined flow rate in the circumferential direction. The ozone thenflows near the surface of an object to be processed (wafer W) and isexhausted from the exhaust port 410a in the ceiling. The heater (heatingresistive element 414) incorporated in the heat plate 412 in the processchamber 410 is electrically connected to a temperature controller 432arranged outside the chamber so that the surface of the wafer W can beheated to a desired temperature under the control of the temperaturecontroller 432.

In the process chamber 410, when the wafer W is exposed to ozone havinga predetermined concentration under a predetermined pressure (reducedpressure) for a predetermined period of time while the wafer W is heatedto a predetermined temperature, oxygen radicals O* produced by thermaldecomposition of ozone properly cause oxidation with an organicsubstance C_(L) H_(M) O_(N) adhering to or contained in the SOG film onthe wafer surface (reaction products CO₂ and H₂ O are exhausted throughthe exhaust port 410a), thereby effectively removing the organicsubstance from the entire surface of the SOG film.

According to the first aspect of this example, an organic SOG film iscoated on a predetermined underlying film, e.g., an SiO₂ film, to apredetermined thickness by a coating step using a general method, e.g.,the spin coating method. The SOG film is then cured in an annealing stepusing a general method, e.g., a heat treatment using a verticalheat-treatment furnace. The surface of the SOG film is flattened by anetching back step using a general method, e.g., a dry etching method ofa cold wall scheme using a CF₄ gas as an etching gas. The resultantwafer W is subjected to an ozone process in the process apparatus ofthis example.

In this case, even after an etching back step, organic substances aredeposited on the surface of the SOG film, and a considerable amount oforganic substance is also left in the SOG film. In this example, adeposition film of organic substances can be properly removed from thesurface of the SOG film of the wafer W, and at the same time, organicsubstances in the SOG film can be effectively removed, thereby improvingthe quality of the SOG, by properly setting process conditions, e.g.,the process surface temperature: 150 to 1,400° C.; the flow rate ofozone: 15 to 30 l/min; the ozone concentration: 5 to 20 wt %; thepressure near the process surface: 200 to 700 Torr; and the processtime: 10 to 180 sec.

As described above, an ozone process in this embodiment allows effectiveremoval of organic substances from the entire SOG film, and hence can beperformed before an etching back step, e.g., after a coating step. Inthis case, in an SOG solution coating step, a drying step of evaporatinga solvent in the SOG solution by heating the SOG solution to about 100to 150° C. (i.e., a pre-baking step) is generally performed, as needed,immediately after the SOG solution is coated. For this reason, it ispreferable that the wafer W be loaded into the process chamber 410 aftersuch a drying step, and an ozone process be performed under the aboveprocess conditions. With this process, the SOG film is cured by anannealing step after organic substances are removed by this ozoneprocess. As a result, inorganic substance Si--O bonds recombine witheach other with longer chains in the SOG film, and good film quality canbe obtained. Furthermore, since no or little organic substance is leftin the cured SOG film, no organic substance is deposited on the surfaceof the SOG film in the next etching back step. Note that an organicsubstance removing step of this example may be performed prior to anetching back step after an annealing step. Moreover, a coating step, anorganic substance removing step, an annealing step, and an organicsubstance removing step may be performed in the order named.

FIG. 27 shows infrared absorption spectra obtained from an SOG filmwhich has undergone an ozone process, and an SOG film which has notundergone an ozone process. In the SOG film (reference) formed withoutundergoing an ozone process, in addition to absorption peaks at --CH₃and CH₃ --Si--CH₃ bonds as organic substances, there are two peaks atinorganic substance bonds, i.e., an O--Si--O bond having a long chainand an Si--O bond having a short chain. In contrast to this, in the SOGfilm formed upon an ozone process according to the example, there are noabsorption peaks corresponding to --CH₃ and CH₃ --Si--CH₃ bonds asorganic substances. In addition, there is no absorption peakscorresponding to an Si--O bond having a short chain as an inorganicsubstance. The absorption peak corresponding to an O--Si--O bondincreases accordingly. That is, according to an ozone process of theexample, when oxygen radicals O* produced by thermal decomposition ofozone react with an organic substance C_(L) H_(M) O_(N) in an SOG film,an organic group (--CH₃) is removed or dissociated, and Si and Orecombine with each other in a portion from which the organic group isremoved. As a result, the chain of the Si--O bond is elongated. Inaddition, in the example, since an organic substance removing process isperformed by a method of removing an organic by means of a chemicalreaction caused by oxygen radicals, an SOG film is free from physicaldamage.

As described above, by performing an ozone process of this embodimentwith respect to an SOG film before or after an annealing step, organicsubstances can be effectively removed from the entire SOG film, i.e.,not only from the film surface but also from the inside of the film,without damaging the SOG film. Even if, therefore, a plasma CVD film isformed on the SOG film in the nest step, the two films exhibit excellentadhesion characteristics, and peeling of the films and the like do notoccur. A stable multilayered wiring structure can be obtained. Note thatthe above description is associated with an organic SOG film. However,the example can also be applied to an inorganic SOG film.

As described above, according to the method of this example, organicsubstances can be effectively removed not only from the surface of anSOG but also from the inside of the film without damaging the SOG film,thereby improving the film quality.

According to the present invention, the above examples can be applied incombination with each other, as needed, in accordance with processsteps.

As has been described above, according to the present invention, thedouble-sided substrate cleaning apparatus comprises a carrier stationfor loading/unloading a carrier in which objects to be processed arestored, a convey mechanism for conveying an object taken out from thecarrier station, at least one cleaning mechanism, arranged along aconvey path on which the convey mechanism conveys the object, forcleaning the object, and an object reversing mechanism, arranged alongthe convey path, for reversing the object. With this arrangement, theapparatus can improve the throughput of various processes.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details, representative devices, andillustrated examples shown and described herein. Accordingly, variousmodifications may be made without departing from the spirit or scope ofthe general inventive concept as defined by the appended claims andtheir equivalents.

What is claimed is:
 1. A method for cleaning both surfaces of asubstrate, comprising:(a) a first cleaning step of conveying a substrateinto a first cleaning mechanism and supplying a treatment liquid to afirst surface of the substrate with a brush kept in contact therewith,so as to clean the first surface, said first surface being a surface onwhich a pattern is to be formed; (b) a second cleaning step of conveyingthe substrate into a second cleaning mechanism and supplying a treatmentliquid to a second surface of the substrate with a brush kept in contacttherewith, so as to clean the second surface, said second surface beinga surface on which no pattern is to be formed, wherein a force withwhich the brush is pressed against the second surface in step (b) isgreater than a force with which the brush is pressed against the firstsurface in said step (a), and wherein the brush used for scrubbing andcleaning the first surface in said step (a) is substantially similar tothe brush used for scrubbing and cleaning the second surface in saidstep (b); and (c) a step of taking the substrate out from one of saidfirst cleaning mechanism and said second cleaning mechanism andreversing the substrate by means of a reversing mechanism locatedoutside of the first and second cleaning mechanisms, and then conveyingthe substrate for cleaning by the other of said first cleaning mechanismand said second cleaning mechanism.
 2. A method according to claim 1,wherein said brushes are rotatably supported by a vertical support shaftduring said steps (a) and (b).
 3. A method for cleaning both surfaces ofa substrate, comprising the steps of:(a) a first cleaning step ofconveying a substrate into a first cleaning mechanism and supplying atreatment liquid to a first surface of the substrate, with a brush keptin contact therewith, so as to clean the first surface, said firstsurface being a surface on which a pattern is to be formed; (b) a secondcleaning step of conveying the substrate into a second cleaningmechanism and supplying a treatment liquid to a second surface of thesubstrate, with a brush kept in contact therewith, so as to clean thesecond surface, said second surface being a surface on which no patternis to be formed, wherein a force with which the brush is pressed againstthe second surface in step (b) is greater than a force with which thebrush is pressed against the first surface in step (a), and wherein thebrush used for scrubbing and cleaning the first surface in said step (a)is substantially similar to the brush used for scrubbing and cleaningthe second surface in said step (b); (c) a step of taking the substrateout from one said first cleaning mechanism and said second cleaningmechanism and reversing the substrate by means of a reversing mechanismlocated outside of the first and second cleaning mechanism, and thenconveying the substrate for cleaning by the other of said first cleaningmechanism and said second cleaning mechanism; and (d) conveying thesubstrate into a heat treatment apparatus after and second surface ofthe substrate are cleaned.
 4. A method according to claim 3, whereinsaid brushes are rotatably supported by a vertical support shaft duringsteps (a) and (b).